Disable FDW support on Postgres 11+ (see bluejekyll#49); created new …

…feature flag

Unfortunately, FDW examples and tests have to be disabled entirely,
because 'examples/fdw' cannot depend on 'pg-extend' crate features.

Cargo.toml

@@ -5,9 +5,10 @@ debug = true
 members = [
     "pg-extend", 
     "pg-extern-attr", 
-    "examples/adding", 
-    "examples/fdw",
-    "examples/fdw-rw",
+    "examples/adding",
+# FDW examples disabled because it's broken with PostgreSQL 11, 12. See https://github.com/bluejekyll/pg-extend-rs/issues/49
+#    "examples/fdw",
+#    "examples/fdw-rw",
     "examples/logging",
     "examples/memory_context",
     "examples/nullable",

integration-tests/tests/fdw.rs

@@ -5,6 +5,9 @@
 // http://opensource.org/licenses/MIT>, at your option. This file may not be
 // copied, modified, or distributed except according to those terms.
 
+// FDW tests disabled because it's broken with PostgreSQL 11, 12. See issue #49
+#![cfg(fdw_is_broken)]
+
 extern crate integration_tests;
 
 use integration_tests::*;

pg-extend/Cargo.toml

@@ -17,9 +17,10 @@ license = "MIT/Apache-2.0"
 build = "build.rs"
 
 [features]
-default = ["postgres-10"]
-postgres-9 = []
-postgres-10 = []
+default = ["postgres-11", "fdw"]
+fdw = []
+postgres-9 = ["fdw"]
+postgres-10 = ["fdw"]
 postgres-11 = []
 
 [dependencies]

pg-extend/src/pg_fdw.rs

@@ -4,6 +4,13 @@
 //! and https://bitbucket.org/adunstan/rotfang-fdw/src/ca21c2a2e5fa6e1424b61bf0170adb3ab4ae68e7/src/rotfang_fdw.c?at=master&fileviewer=file-view-default
 //! For use with `#[pg_foreignwrapper]` from pg-extend-attr
 
+// FDW on PostgreSQL 12 is not supported yet :(
+#![cfg(feature = "fdw")]
+
+// If anyone tries to enable "fdw" feature with newer Postgres, throw error.
+#[cfg(any(feature = "postgres-11", feature = "postgres-12"))]
+compile_error!("pg-extend-rs does not support FDW on PostgreSQL 11 or newer. See https://github.com/bluejekyll/pg-extend-rs/issues/49");
+
 use std::boxed::Box;
 use std::collections::HashMap;
 use std::ffi::{CStr, CString};